.bordered {
  border: 1px solid black;
}
#app {
  width: 500px;
  height: 500px;
  background-color: red;
  margin: 10px auto;
  border: 1px solid black;
}
#app h1 {
  color: bisque;
}
.logo-img {
  width: 100px;
  border: 1px solid black;
  background-color: #efefef;
  border-radius: 50%;
  padding: 5px;
}
::after {
  display: block;
  content: "hello world";
  width: 100px;
  height: 100px;
  border: 1px solid black;
}
.box {
  width: calc(50% + (50vh/2 - 20px));
  border: 1px solid black;
  height: 100px;
}
